The invention relates to a flat composite body as a vehicle body element with an asymmetric laminar structure consisting of a first outer layer of an aluminum material, a steel sheet, or a sintered metal sheet, also consisting of an intermediate layer, in particular a foam core, and a second inner layer of a non-metallic material.
The invention also relates to a process for manufacture of such a flat composite body.
A generic composite body and accordingly a process for manufacture of such composite body is known from the essay xe2x80x9cConsiderations relating to large-series use of sandwich components, their design and configuration, based on the example of the AUDI research vehicle hoodxe2x80x9d in the series of status BMFT [German Federal Ministry of Research and Technology] status reports xe2x80x98Development trends for motor vehicles and fuels,xe2x80x99 Research Survey 1982, pages 167-177, published by Txc3x9cV Rheinland. The essay concerns itself with light-weight construction in a sandwich design, using a motor vehicle hood as an example. Design, configuration, and manufacturing considerations indicate the possibilities and limits of this light-weight construction principle. Various exemplary embodiments are shown on pages 171 and 172 in connection with the laminar design. In one of the embodiment examples the cover layers consist of aluminum or laminated sheet metal and plastic. This results in an asymmetrical laminar design. The core consists preferably of Structhan (thermoreactive, foamed, fiberglass-reinforced plastic of variable specific gravity). Structhan assumes the function of stress equalization (prevention of warping).
DE 39 534 C2 describes a process and a support mould for manufacture of plates and platelike articles such as doors, in particular refrigerator doors. An asymmetric laminar design is created in this instance as well, with a sheet metal covering layer on one side and a sheet plastic covering layer on the other and a hard cellular material expanded in situ from a liquid reaction mixture between these two layers. An effort is made to counter the danger of warping due to different thermal expansion coefficients by subjecting the sheet metal cover layer and/or the sheet plastic cover layer before expansion to one of the preshaping processes which offsets and counteracts the warping which occurs during cooling. The warping that occurs is not subject to calculation and must be determined empirically.
For the sake of clarity, reference is made to WO 83/00840 which describes a composite body, in particular a composite plate for the construction of ship walls, container walls or the like with a double-sided rigid outer layer, a one-part or multi-part foam-core and fiber-reinforced intermediate layers made of fiberglass or the like between each outer layer and core as well as hardened plastic for connecting the entire arrangement. Thereby a symmetrical design is achieved in which each outer layer consists of a material with a compressive strength of approximately at least that of high-grade aluminum.
On this basis the object of the invention is to prepare a flat composite body as a vehicle body element with an asymmetrical laminar structure of low weight accompanied by high dimensional stability and high rigidity, along with good paintability.
The solution claimed for the invention lies in a flat composite material asymmetric in structure having the characteristics specified in claim 1. Claim 7 specifies a process especially well suited for manufacture of such a material. Advantageous configurations and developments of the invention are specified in the relevant subsidiary claims.
The invention is explained in detail with reference to an embodiment of such a flat composite material, an especially well suited instance of application of which is a self-contained passenger car body part such as a hardtop.